Really weird one yesterday. I signed up for a group ride of just over 20 miles. After about five miles or so, the entire remainder of the field vanished (into the ether, not up the road as usual!) I was left as the only rider on the name board as well. So I did the remaining fifteen miles on my own. With a mile to go, all the names came back. I still couldn't see anyone, but there was no-one within 30 seconds of me anyway, either in front or behind, which probably explains that.
Bit of a washout as a group ride, even if the ride itself was OK.